Newbie Question: Conflicting WANs

[Lv9EmbnMpsQSCT3]

I have an ASUSTOR 5304T NAS with 4x2Tb SSDs. When I go to System Information > Network in the ADM the WAN is listed as one address, say, for example, 22.101.81.192 (a completely made-up WAN address). My ASUS router, however, lists my WAN as a different IP address, for example, 100.80.192.204. When I go to Settings > Manual > DDNS and Enable DDNS Service the Network Status at the bottom of that page again lists the WAN IP and the Last Checking IP as 22.101.81.192 and SUCCESS for the last DDNS update. When I click the EZ-Router tab I get a message in red that states: "Multiple routers detected. The router's external IP is different than the NAS's external IP. Please check your network environment first."
I am unable to access any of the services of the NAS from outside of my home network and I am assuming it may be due to this conflict in WAN IP addresses. Several questions:
1. Am I correct in assuming my inability to access the NAS from outside of my home network is because of this conflict in WAN IP addresses?
2. My router is connected to the modem provided by my internet service provider. My router lists the WAN IP address as different from what my NAS reads as the WAN IP address. Why is this happening?
3. If this is indeed the cause of me not being able to access the NAS from the world outside of my home network how the heck to I rectify this conflict.

Apologies in advance for my lack of use of technical jargon in describing this problem. If anyone can shed some light on this it would be greatly appreciates!

Thanks!
MFM

[orion]

Yes, it is highly possible that there are more routers inside your service provider. You can easily check your real external IP: https://www.myexternalip.com/

If you plan to open NAS services to internet, you'll need to discuss with your ISP to allocate a static IP address. However I won't recommend you to do that. It's dangerous to public your NAS to internet (except you know how to setup network security well).

On the other hand, you should try to enable EZ connect and install AEC software in your PC (outside your home). You can then access your data outside your home (although network bandwidth is shared and limited).

[Lv9EmbnMpsQSCT3]

Thank you very much. I shall work on the EZ connect/AEC software solution.